Device for driving the platen of a typewriter



Oct. 29, 1957 E. ASCOLI 2,811,236

DEVICE FOR DRIVING THE PLATEN OF A TYPEWRITER Filed May 21, 1956 Z 6% EZ 3 1 1 i 3.

A Y 7* 1 H E] E g n- United States Patent DEVICE FOR DRIVING THE PLATENOF A TYPEWRITER Enzo Ascoli, Yverdon, Switzerland, assignor to PaillardS. A., Sainte-Croix, Switzerland, a corporation of SwitzerlandApplication May 21, 1956, Serial No. 586,306

Claims priority, application Switzerland July 5, 1955 1 Claim. (Cl.197-114) The rotatable driving of the platen of a typewriter is effectedby means of a line spacing mechanism, controlled either manually, by theline spacing lever, or electrically. These movements of rotation impartaccelerations to the sheets of paper passing around the platen, at thecommencement of each movement, and decelerations (negativeaccelerations) when stopping against stops.

The forces of acceleration thus created are opposed by frictional forcespresent between the sheets and the platen and between the sheets and theinterposed carbon sheets, so as to prevent a possible slipping of thesheets relatively to the platen, or between said sheets. It is ob viousthat when the forces of acceleration exceed the frictional forces, saidslipping becomes unavoidable, as a result of which a defective movementof the paper occurs.

The frictional forces depend, on the one hand, on the pressure occurringbetween the sheets and the platen, and between the sheets themselves,and on the other hand, on the coeflicients of friction. Whilst thepressure, which depends on the driving rollers, is controlled easily,this is not the case as regards the coefiicients of friction which varywith the quality of the paper, as also with the temperature, humidityand so forth.

On the other hand, the forces of acceleration vary, in the case ofmanual typewriters, from one user to another, which renders theircontrol difficult.

Amongst the vertical forces of acceleration, due to angular movements ofthe platen, horizontal forces are also due to the movements of thecarriage. However, the action of said latter is more effectivelyovercome, in particular by the friction between the driving rollers andthe papers, said friction in the vertical direction being replaced by amuch weaker resistance to rolling.

But, as is well known, the value of frictional resistance (at rest)decreases rapidly when, as a result of the move ment, it is convertedinto sliding friction. Thus, when the sliding movement of the paper isreduced by the action of vertical forces of acceleration, the horizontalforces of acceleration may produce a horizontal sliding, even when bythemselves, they are not capable of doing this.

From the foregoing it will be seen that it is indispensable, for thecorrect movement of the paper, to maintain the vertical forces ofacceleration, due to angular movements of the platen, below the valuewhich can cause a slipping of the paper.

The subject of the present invention is a driving device for the platenof a typewriter, comprising a line spacing mechanism, characterised inthat the said mechanism is connected to the platen by means of aresilient coupling adapted to deaden the shocks at the beginning andstopping of each angular movement of the platen, in such a manner as toreduce the forces of acceleration acting on the paper.

One form of construction of the device according to the invention isshown diagrammatically and by way of example in the accompanyingdrawing.

The platen 1, provided at each of its ends with a hub 2, 3,respectively, is mounted on a shaft 4 turning in bearings 5 and 6provided in the chassis of the carriage of a typewriter (not shown). Theplaten 1 is secured angularly to the shaft 4 solely at one of its ends,particularly by the hub 3, by means of screws 7. The other end of theplaten, particularly the hub 2, can turn freely on the shaft 4. Aratchet wheel 8, forming part of the line spacing mechanism, is securednear the end of the shaft located opposite its point of securing to theplaten.

To each of the ends of the shaft 4 is secured an operating knob 9, 10,respectively.

It will be readily understood that, when the driving of the platen inrotation is efiected through the medium of the line spacing mechanism(wheel 8), the shaft 4 operates in the manner of a torsion bar, so thatit constitutes an elastic clutch between the said mechanism and theplaten, enabling the shocks, at the starting and stopping of eachangular movement of the latter to be deadened and, consequently reducingthe forces of acceleration acting on the paper.

I claim:

In a typewriter, means for rotatably driving a platen and controllingundesirable movement thereof comprising, a resilient, axially disposedshaft passing through said platen, a line spacing mechanism connected tosaid shaft at one end thereof, said platen being rigidly secured to saidshaft at the end opposite said line spacing mechanism, and being freelyrotatable on said shaft at the end adjacent said line spacing mechanism,whereby said shaft acts as a torsion bar to control the shocks resultingfrom the actuation of said line spacing mechanism and thereby avoidsinaccurate line spacing.

References Cited in the file of this patent UNITED STATES PATENTS1,121,971 Brown Dec. 22, 1914

